IgE-mediated mast cell degranulation and recovery monitored by time-lapse photography

Background: Mast cells are long-lived resident cells that are of great importance in an allergic reaction. It has previously been suggested that after IgE-mediated degranulation mast cells can undergo regranulation. Such a process is probably of great importance with respect to the severity and perpetuation of the allergic response. Objective: Our purpose was to investigate whether mast cells recover from degranulation and whether they still have the potential to release a granule-associated mediator and upregulate certain cytokine genes. Methods: Mouse mast cells were repeatedly activated by IgE and specific antigen with a 24-hour or 48-hour interval. During each of the 2 activation stages, release of beta -hexosaminidase was measured by means of enzymatic colorimetric analysis, and IL-13 and IL-6 mRNA was detected by ribonuclease protection assay. Both scanning electron microscopy and time-lapse photography were used to reveal the process of mast cell recovery. Results: We found that re-activation of degranulated mast cells in response to high-affinity IgE-receptor cross-linkage triggers beta -hexosaminidase release and upregulation of IL-13 and IL-6 gene expression levels similar to what is seen in the initial activation. Scanning electron microscopy documented cells at various stages during the recovery process 30 minutes after the activation. With time-lapse photography, a single cell that had undergone degranulation could be visualized consecutively during its recovery process. Conclusion: Mast cells can recover after an IgE-mediated activation and can repeatedly release beta -hexosaminidase and express IL-6 and IL-13 mRNA after re-activation.